Israelis have come to a mournful, two-minute standstill as sirens pierced the air in remembrance of the 6 million Jews killed in the Nazi Holocaust during World War II.

Israel's annual Holocaust memorial day, marked Thursday, is one of the most solemn on the nation's calendar.

As the siren sounded, cars and buses pulled over on the side of highways and roads. Motorists stepped out of their cars and pedestrians stopped in their tracks, bowing their heads as they remembered those who perished.

Melancholic music and interviews with Holocaust survivors are filling the airwaves while TV stations show documentaries about the genocide.

Ceremonies are held around the country. Names of those killed are read out at parliament later in the day.

U.S. President Barack Obama condemned anti-Semitism in a statement on Holocaust Remembrance Day.

"Together we must firmly and forcefully condemn the anti-Semitism that is still far too common today," the statement said. "Together we must stand against bigotry and hatred in all their forms."

U.S. Secretary of State John Kerry also issued a statement in honor of the observance. "We bow our heads as we both mourn and honor the six million Jews who perished in the most painful and horrific chapter in human history," he said.

"We lack the power to rewind the clock or to bring back those who were murdered," the statement said. "But we do have the power of remembrance, and we will never cease to honor the memory of those who were killed, to grieve their loss, and to cherish their names."